In a typical lancing apparatus, a lancet holder holding a lancet is accommodated in a housing to which a front end cover is attached. When a predetermined operation is performed, the lancet holder advances toward the front end of the front end cover by a spring force. Since the lancet is generally disposable, the front end cover is made removable so that it can be removed in attaching or detaching the lancet. In using the lancing apparatus, the front end cover is pressed against skin of the human body. The front end cover is formed with an opening for allowing the needle to lance the skin. When the lancet holder is advanced, the lancet passes through the opening to lance the skin.
For example, blood is extracted from the fingertip or the forearm. Although, the fingertip bleeds easily, lancing of the fingertip involves relatively strong pain. On the other hand, although the forearm is unlikely to bleed, the pain in lancing is relatively small. Further, the tendency to bleed from the skin varies among individuals at any portion of the skin. Preferably, therefore, the portion of the skin for extracting blood is selected based on the user's preference or in consideration of the tendency to bleed. In extracting blood from the forearm, it is preferable to bulge the skin by suction and to lance the bulged skin for promoting bleeding.
However, when the same front cover is used for the blood extraction from the fingertip and that from the forearm, proper blood extraction may not be performed in the following reasons.
When a front end cover with a relatively large opening is pressed against the fingertip, the finger tip bulges. The amount of bulging differs among individuals because of the variations of the hardness of the skin. Therefore, the positional relationship between the needle of the lancet and the skin, and hence, the lancing depth differ among individuals, which hinders stable lancing operation. To eliminate such a problem, it is desirable to use a front end cover with a relatively small opening. On the other hand, in extracting blood from the forearm, it is preferable to bulge the skin by suction, as noted above. For this purpose, it is preferable to use a front end cover with a relatively large opening. Further, when a lancing apparatus having a manual suction mechanism is used, the positional relationship between the lancing apparatus and the skin is likely to deviate due to the vibration of the lancing apparatus during the suction. To perform stable lancing operation by preventing such deviation, the adhesion between the front end cover and the skin need be enhanced. Also for this purpose, it is preferable to use a front end cover with a relatively large opening.
As noted above, it is preferable to use a front end cover with a relatively small opening for the blood extraction from the fingertip, whereas it is preferable to use a front end cover with a relatively large opening for the blood extraction from the forearm. In the conventional lancing apparatus, however, the size of the opening of the front end cover is fixed. Therefore, to properly perform both of the blood extraction from the fingertip and that from the forearm, the user need to prepare a plurality of lancing apparatuses, i.e. one for the fingertip and one for the forearm, for example. Such preparation and use of a plurality of lancing apparatuses is inconvenient for the user and puts the financial burden on the user. However, with a single kind of lancing apparatus, proper blood extraction is possible only from a single particular portion, which is inconvenient.
In lancing the skin with a lancet by utilizing a lancing apparatus, it is desirable that the amount of lancing in the skin is adjustable for minimizing the pain the user feels and for preventing excessive or insufficient bleeding from the skin. For instance, WO97/04707 A1 discloses lancing assembly in which the lancing depth is adjustable. Specifically, the disclosed assembly includes an injector for launching a lancet, a cap attached to the injector and engageable with the lancet, a cover for coming into contact with the skin in lancing, and an adjuster for adjusting the distance between the cap and the cover. In this assembly, the distance between the cap and the cover is adjustable by turning the adjuster, whereby the lancing depth can be adjusted.
However, the lancing depth adjustment mechanism of the assembly requires three parts, i.e. the cap, the cover and the adjuster in addition to the injector. Such a large number of parts leads to an increase in the manufacturing cost. Moreover, in this assembly, the lancet is attached to the injector in a state separated from the assembly, and then the assembly is attached to the injector. Therefore, even when the lancing depth need be adjusted due to e.g. the change of the position to be lanced, the user may attach the assembly to the injector and launch the lancet without adjusting the lancing depth. In such a case, an excessive or insufficient amount of blood may be extracted or the user may suffer discomfort.